PS1003 Andrew: Sensation and Sensory Processing II Flashcards
What is the primary auditory pathway?
Cochlea- in the ear. Travels through the vestibulo-cochlear nerve (CN V III). Tthis projects to the cochlear nuclues, and then the superor olivary nucleus at the pons where there is cross over. (After this point it is binaural- so comes from both ears). It than travels to the inferior colliculus and then the medial geniculare nucleus as the thalamus finally to the auditory cortex.
What is the Cochlea?
The sense organ in the ear
What happens in the cochlea?
sound waves are converted into vibration in the basilar membrane.
What is the organ of corti which is located in the the cochlea?
It is the sensitive element in the inner ear and can be thought of as the body’s microphone.
What does the hair cells in the organ of Corti do?
It transduces movement of basilar membrane into electrical signal.
What is the basilar membrane?
The basilar membrane within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani
Where is high frequency sound transduced?
At the base of the cochlea
What is low frequency sound transduced?
At the apex of the cochlea
Where is sound transmitted along?
the vestibule-cochlear nerve
Where does auditory processing take place?
It was originally thought to be in auditory cortex, however found that the initial processing occurs in pons and thalamus.
Where is the dorsal stream in auditory processing?
The parietal lobe
What is the dorsal stream responsible for in auditory processing?
Spatial analysis- where the sound is coming from- able to locate the sound (where)
What is the ventral stream in auditory processing?
Temporal lobe
What is the ventral stream in auditory processing responsible for?
Component analysis- analysis of what the sound is (what)
What is one cause of deafness: Conduction deafness
disorders of the outer or middle ear, which prevent sound vibrations reaching the cochlea
What is one cause of deafness: Sensorineural deafness
an inability of the auditory nerve fibres to be excited in the normal manner
What is one cause of deafness: Central deafness
damage to auditory brain centres and seldom a simple loss of hearing
What is the localisation of sound dependent?
It is dependent on different characteristics of a sound arriving at each ear
Localisation of sound: what is intensity difference?
difference in intensity of the sound between the two ears
Localisation of sound: what is latency?
Phase shift between the two ears- due to the slight
What is the duplex theory?
Sound location depends on a combination of intensity and latency
What information does the vestibular organ recieve?
Sensory information about motion, equilibrium, and spatial orientation is provided by the vestibular apparatus, which in each ear includes the utricle, saccule, and three semicircular canals.
What do the semi-circular in the vestibular organ do?
detect head rotation and tilt around three axes
What is the pathway for detecting head movement?
Head movement- movement of endolymph- displacement of capula- stimulation of hair cells- activation of CN VIII- information transmitted to brain
What and where is endolymph?
Endolymph. Cross-section of cochlea. (Endolymph is located in the cochlear duct - the light green region at the middle of the diagram.) Endolymph is the fluid contained in the membranous labyrinth of the inner ear.
What is the cupula?
vestibular system: sense of spatial orientation
What is CN VIII?
The crainal nerve VIII, also known as the Vestibulocochlear nerve and brings sound and information about one’s position and movement in space into the brain.
What are the vestibular pathways?
information comes in through the CN VIII (vestibulocochlear nerve) this is processed through the vestibuler nuclei in the brainstem (and motor thalamus) to the vestibulo ocular reflex, as well. CN VIII information also goes through the cerebellum to the cortex (which has info from the motor thalamus) to the balance reflex
What is the vestibulo-ocular reflex?
The vestibulo-ocular reflex. A rotation of the head is detected, which triggers an inhibitory signal to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes. Basically helps to track movement.
How are the vestibulo-ocular reflex and balance reflex different from normal reflexes?
They are not just through the spinal cord but though centres of control (e.g. cortex) however we still do not need to think about the action.
What is the balance reflex?
Postural reflexes are responsible for the subconscious maintenance of the body’s posture when movement and position is altered and they ensure that the body remains upright and aligned. It is the effects of gravity on the body which triggers their response and so these reflexes do not begin to develop until after the baby is born.
What is the balance reflex pathway?
vestibular organ feeds into the vestibular nuclei which is spilt into two areas, medial (closer to the midline) this controls neck muscles and therefore head orientation. The second area is lateral (further from the midline), therefore control peripheral muscles which is in charge of postural muscles and balance.
How is motion sickness caused?
May be caused by a mismatch between visual information and information from the vestibular organ- similar to that of an ear infection but in that case the information the vestibular organ is receiving is incorrect due to infection
What are the sensory receptors pathways?
The sensory receptors that are for peripheral goes through the spinal cord and that in the cranial (e.g. tongue) feeds into the brain stem. Project to the thalamus, to the somatosensory cortex which then goes to either the cingulate cortex of other `cortical areas.
Where is the somatosensory cortex located?
It is a band of tissue around the post central gyrus, which is behind the central sulci and at the front of the parietal lobe.
How are the motor and somatosensory homunculus similar?
The tongue and hands are very sensitive.
What are peripheral sensory receptors?
They are free nerve endings (pain and temperature). It is the skin which has specific receptors
What is the Merkel’s disc?
Responsible for touch and deep pressure
what is the Meissner’s corpuscle?
Responsible for touch and things on the skin- so very light and sensitive
What is the pacinian corpuscle?
Responsible for vibration- so movement along the skin
What is the Ruffini’s ending responsible for?
Responsible for stretch, so the stretching of skin at the fingers for example when they move
What are hair follicle receptors responsible for?
The detection of movement of hair.
what is a Nociception?
the perception of a noxious stimulus- an objective measure
what is pain?
the subjective ‘feeling’ due to a noxious stimulus
What is analgesia?
the modulation of nociception or pain
Why is pain subjective?
Because people have different pain thresholds and this also differs within an individual over time.
Nociception: what is transduced?
Transduction of of a noxious stimulus into electrical activity in appropriate nerve endings e.g might be temperature so aware that something is hot